CVE-2026-93601
LowCVSS 2.2Summary
rustls-webpki versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accept permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com is treated as satisfied by a certificate for *.example.com, which could assert reject.example.com outside the permitted subtree.
Risk Assessment
This may allow bypassing name constraints and trusting a certificate that should be rejected, potentially enabling man-in-the-middle attacks. Exploitation requires a misissued wildcard certificate.
Recommendation
Update rustls-webpki to version 0.103.12 or 0.104.0-alpha.6 or later. Ensure certificates used are properly issued and do not rely on incorrect name constraints.
Other vulnerabilities in rustls-webpki
See all- CVE-2026-93602Medium
rustls-webpki versions before 0.103.10 and 0.104.0-alpha.5 contain faulty CRL authority-matching logic that compares only the first distributionPoint against each CRL's IssuingDistributionPoint, ignoring additional distributionPoints.
- CVE-2026-93600Low
rustls-webpki versions 0.101.0 through 0.103.11 and 0.104.0-alpha releases before 0.104.0-alpha.6 ignore X.509 name constraints that apply to URI names, accepting rather than enforcing them. These constraints apply to otherwise properly issued certificates, so the flaw is reachable after successful signature verification and requires a misissued certificate.
- CVE-2026-93599High
rustls-webpki through 0.103.12 (and 0.104.0-alpha releases before 0.104.0-alpha.7) contains a reachable panic in bit_string_flags() in src/der.rs. The input guard fails to reject a named-bit BIT STRING with content exactly [0x00], causing an underflow and panic. Reachable via BorrowedCertRevocationList::from_der() when a CRL contains an issuingDistributionPoint extension with such an onlySomeReasons value. Requires an application that opts in to CRL revocation checking and parses attacker-influenced CRL bytes; default rustls configuration is unaffected. Fixed in 0.103.13 and 0.104.0-alpha.7.
Original NVD description (English source)
rustls-webpki (the Rust webpki fork used by rustls) versions >= 0.101.0 and prior to 0.103.12 and 0.104.0-alpha.6 incorrectly accepted permitted-subtree DNS name constraints for certificates asserting a wildcard name. For example, a name constraint of accept.example.com was treated as satisfied by a certificate for *.example.com, which could feasibly assert reject.example.com — a name outside the permitted subtree. Because name constraints are restrictions applied to otherwise properly issued certificates, the issue is only reachable after signature verification succeeds and requires a misissued wildcard certificate to exploit.